Shank-3-Deficient Rat Model
Attentional deficits in Shank-3 deficient rat model
Attention deficits are often associated with both PMS and ASD. Thus, we assessed performance in the attentionally demanding 5-choice serial reaction time (5-CSRT) task in which rats must respond quickly to briefly presented light cues (Fig. 1A). Both the Shank3 Het and KO rats learned the task and were able to reach baseline, similar to WT controls (criteria were accuracy rates higher than 80% for two consecutive days with omission rates lower than 20%). However, both the Shank3 Het and KO rats had lower accuracy and lower omission rates, when compared to WT rats, even upon extensive training. Moreover, after reaching baseline criterion Shank3-deficient rats did not maintain even this level …show more content…
of performance across the 10-day test period, during which they performed significantly fewer correct trials, made more errors, and exhibited higher omission rates than WT rats (Fig. 1B-D). Even on trials with a correct response, Shank3-deficient rats responded more slowly and with more variable latencies than WT rats (Fig. 1E). Fig. 1. Shank3-deficient rats exhibit deficits in attention.
(A) Scheme represents the setup inside the touch screen chambers used in the 5-CSRT task to test attention. (B) Traces and clouds indicate average percent of trials with a correct response ± SEM. (WT, n=10; Het, n=13; KO, n=12) across ten 5-CSRT sessions. Right side is the cross-rat median (dot) and middle quartiles (vertical lines). (C) Traces represent mean percentage of trials where an incorrect response was made. (D) Mean percentage of trials with no cued response. (E) Average reaction times on trials with a correct response. Results were observed in two independent cohorts; therefore the results were pooled and presented here as a combined cohort. *P<0.001. Along with the attentionally demanding 5CSRT task, we proposed a novel behavioral task to help record neural events like VEP from EEG recording without any confounding effects from anesthesia or higher anxiety levels induced in physical restraint. The VEP behavioral task simply involved breaking of a photo beam to onset the pattern reversal of the stimulus presented on the screen, which would invoke VEPs in the visual cortex (Fig.3) Fig. 2. Proposed behavioral task for VEP recording.
Scheme represents the setup inside the touch screen chambers used in the 5-CSRT task to test attention.
The stimulus to be presented to invoke VEPs in the rats were created using the information on rat’s visual system [references] in R-Statistical software and were of two traditionally used categories: Vertical Bars and Checkerboard patterns. The pixel size for checkerboard pattern and the vertical bar width was suggested by modifying the information of human VEP protocols size for the rats based on the rat visual system information. (STIMULUS).
The raster plot of the behavior responses recorded for the proposed task for VEP recording also showed similar slow responses when the time period between the pattern reversal onset and the capacitive screen touch was reduced from 2sec to 1sec (RASTER).
In summary, these results indicate that Shank3-deficient rats are impaired in an attentional task, which, when considered together with the documented deficits in long-term social memory [refer submitted paper], suggests that this model demonstrates face validity with major features of PMS and ASD. Also, the preliminary behavior data of the proposed behavioral task to record neural events like VEP shows promising applicability that it can serve as a viable alternative to the existing VEP protocols, however, further calibration of the behavioral tasks, like inclusion of a random non-reversal of the stimulus to show a robust the rat’s attention to the stimulus and to eliminate the possibility of the behavioral response being perseverative in nature, is necessary to be implemented for its future employment. DISCUSSION:
One of the major goals of this study was to provide face validity of the rat model for PMS using an attentionally demanding task and determine whether the phenotype can be rescued by using pharmaceutical intervention.
When PMS is diagnosed as ASD, behavioral and psychological treatments are considered the first line of the intervention strategy [45]. Pharmacological treatments of the core and often devastating deficits in ASD do not exist. Recently, the field has begun to translate basic neurobiological findings gleaned from mouse models into promising pharmacological treatments for a host of genetic disorders such as Fragile X syndrome, Tuberous sclerosis, Rett syndrome, and PMS [46-49]. Genetically modified rat models are especially valuable for behavioral and functional studies. They have several species-specific advantages over mouse models, including a more complex behavioral repertoire and larger brains that readily facilitate high-density electrophysiological recordings. Moreover, rats remain the primary choice of the pharmaceutical industry for studying the pharmacokinetic (PK) properties of novel drugs that may have therapeutic potential. Our results demonstrate that Shank3 deficiency in rat impairs its attention while performing visually attentive and demanding tasks. Deficits in such tasks may be a result of blunted synaptic plasticity, where brief events must be rapidly encoded and reliably stored by neural circuits to promote appropriate and timely behavior. Since pharmacological treatments for such fundamentally severe deficits in ASD do not exist, the results we found provides oxytocin as a potential therapeutics. Our results show for the first time, a beneficial effect of oxytocin on attention to brief stimuli. Attentional deficits are often co-morbid in attention-deficit disorder (ADHD) and ASD, [52] which is perhaps reflective of a shared etiology between the ASD and may explain why oxytocin improved both deficit types in Shank3 deficient rats. We
also established that the proposed behavioral task and the novel design of the insert promotes instinctive behavior in rats, suggesting that such natural behavior can be exploited to record anesthesia-free, non-restraint VEP recordings.
In summary, we found that oxytocin treatment ameliorates the attentional deficits in Shank3-deficient rats, which suggests that stimulation of the oxtytocinergic system might be one of the biological system resulting in the PMS phenotypic symptoms and can be a potential therapeutic target in human PMS patients. Additionally, the novel design Based on these findings, the Shank3-deficient rat model, to our knowledge, demonstrate face validity such that it can be expected to pave the way for future studies, using this model, to investigate the mode by which Shank3 mutations affect brain activity during behavior and to further study the effects of6 oxytocin and other potential therapeutics.
Attention deficits are often associated with both PMS and ASD. Thus, we assessed performance in the attentionally demanding 5-choice serial reaction time (5-CSRT) task in which rats must respond quickly to briefly presented light cues (Fig. 1A). Both the Shank3 Het and KO rats learned the task and were able to reach baseline, similar to WT controls (criteria were accuracy rates higher than 80% for two consecutive days with omission rates lower than 20%). However, both the Shank3 Het and KO rats had lower accuracy and lower omission rates, when compared to WT rats, even upon extensive training. Moreover, after reaching baseline criterion Shank3-deficient rats did not maintain even this level …show more content…
of performance across the 10-day test period, during which they performed significantly fewer correct trials, made more errors, and exhibited higher omission rates than WT rats (Fig. 1B-D). Even on trials with a correct response, Shank3-deficient rats responded more slowly and with more variable latencies than WT rats (Fig. 1E). Fig. 1. Shank3-deficient rats exhibit deficits in attention.
(A) Scheme represents the setup inside the touch screen chambers used in the 5-CSRT task to test attention. (B) Traces and clouds indicate average percent of trials with a correct response ± SEM. (WT, n=10; Het, n=13; KO, n=12) across ten 5-CSRT sessions. Right side is the cross-rat median (dot) and middle quartiles (vertical lines). (C) Traces represent mean percentage of trials where an incorrect response was made. (D) Mean percentage of trials with no cued response. (E) Average reaction times on trials with a correct response. Results were observed in two independent cohorts; therefore the results were pooled and presented here as a combined cohort. *P<0.001. Along with the attentionally demanding 5CSRT task, we proposed a novel behavioral task to help record neural events like VEP from EEG recording without any confounding effects from anesthesia or higher anxiety levels induced in physical restraint. The VEP behavioral task simply involved breaking of a photo beam to onset the pattern reversal of the stimulus presented on the screen, which would invoke VEPs in the visual cortex (Fig.3) Fig. 2. Proposed behavioral task for VEP recording.
Scheme represents the setup inside the touch screen chambers used in the 5-CSRT task to test attention.
The stimulus to be presented to invoke VEPs in the rats were created using the information on rat’s visual system [references] in R-Statistical software and were of two traditionally used categories: Vertical Bars and Checkerboard patterns. The pixel size for checkerboard pattern and the vertical bar width was suggested by modifying the information of human VEP protocols size for the rats based on the rat visual system information. (STIMULUS).
The raster plot of the behavior responses recorded for the proposed task for VEP recording also showed similar slow responses when the time period between the pattern reversal onset and the capacitive screen touch was reduced from 2sec to 1sec (RASTER).
In summary, these results indicate that Shank3-deficient rats are impaired in an attentional task, which, when considered together with the documented deficits in long-term social memory [refer submitted paper], suggests that this model demonstrates face validity with major features of PMS and ASD. Also, the preliminary behavior data of the proposed behavioral task to record neural events like VEP shows promising applicability that it can serve as a viable alternative to the existing VEP protocols, however, further calibration of the behavioral tasks, like inclusion of a random non-reversal of the stimulus to show a robust the rat’s attention to the stimulus and to eliminate the possibility of the behavioral response being perseverative in nature, is necessary to be implemented for its future employment. DISCUSSION:
One of the major goals of this study was to provide face validity of the rat model for PMS using an attentionally demanding task and determine whether the phenotype can be rescued by using pharmaceutical intervention.
When PMS is diagnosed as ASD, behavioral and psychological treatments are considered the first line of the intervention strategy [45]. Pharmacological treatments of the core and often devastating deficits in ASD do not exist. Recently, the field has begun to translate basic neurobiological findings gleaned from mouse models into promising pharmacological treatments for a host of genetic disorders such as Fragile X syndrome, Tuberous sclerosis, Rett syndrome, and PMS [46-49]. Genetically modified rat models are especially valuable for behavioral and functional studies. They have several species-specific advantages over mouse models, including a more complex behavioral repertoire and larger brains that readily facilitate high-density electrophysiological recordings. Moreover, rats remain the primary choice of the pharmaceutical industry for studying the pharmacokinetic (PK) properties of novel drugs that may have therapeutic potential. Our results demonstrate that Shank3 deficiency in rat impairs its attention while performing visually attentive and demanding tasks. Deficits in such tasks may be a result of blunted synaptic plasticity, where brief events must be rapidly encoded and reliably stored by neural circuits to promote appropriate and timely behavior. Since pharmacological treatments for such fundamentally severe deficits in ASD do not exist, the results we found provides oxytocin as a potential therapeutics. Our results show for the first time, a beneficial effect of oxytocin on attention to brief stimuli. Attentional deficits are often co-morbid in attention-deficit disorder (ADHD) and ASD, [52] which is perhaps reflective of a shared etiology between the ASD and may explain why oxytocin improved both deficit types in Shank3 deficient rats. We
also established that the proposed behavioral task and the novel design of the insert promotes instinctive behavior in rats, suggesting that such natural behavior can be exploited to record anesthesia-free, non-restraint VEP recordings.
In summary, we found that oxytocin treatment ameliorates the attentional deficits in Shank3-deficient rats, which suggests that stimulation of the oxtytocinergic system might be one of the biological system resulting in the PMS phenotypic symptoms and can be a potential therapeutic target in human PMS patients. Additionally, the novel design Based on these findings, the Shank3-deficient rat model, to our knowledge, demonstrate face validity such that it can be expected to pave the way for future studies, using this model, to investigate the mode by which Shank3 mutations affect brain activity during behavior and to further study the effects of6 oxytocin and other potential therapeutics.